1. Field of the Invention
The present invention generally relates to sports devices and more particularly to improved archery arrows having improved piles.
2. Prior Art
Conventional archery arrows include elongated usually hollow shafts fitted at their rear ends with string nocks and at their front ends with arrow piles. Such arrow piles usually include an elongated hollow tube releasably affixed to the front end of the arrow shaft and a point connected to the front end of the pile tube. The size and shape of the points vary, depending on the type of arrow and the use to which it is to be put. Thus, for hunting purposes, broadheads may be used. For field archery, field or target points are suitable. For target archery target points are used. Whatever the shape of the points, they usually end in a sharp tip, although even this is not the case for so-called blunts. Most commonly used are the target points which have outer surfaces which are cone-shaped. Thus, in outline, the edges of the point run in straight lines from the apex or tip to the base or rear end of the point. Such points cause the air being passed through during arrow flight to tend to flow outwardly away from the arrow shaft. This is also the case with field points, which are curved inwardly over part of their length and with most other arrows.
A variety of shapes have been utilized for arrow vanes and points and various combinations of shaft diameters, lengths and thicknesses, all with a view toward improving arrow flight, speed and accuracy. Further improvements are desired. For example, it is known that arrow speed has an influence on accuracy of shooting. Thus, a higher arrow speed means a flatter trajectory which in turn means a greater effective target area, resulting in higher scores. Higher arrow speed can be achieved by increasing the draw weight of the archery bow, but when this is excessively increased the increased muscular effort to shoot the bow reduces accuracy in a long tournament. Arrow speed is also dependent on the particular construction of the bow. Accordingly, selection of a "faster" bow at a given draw weight can increase arrow speed. Moreover, the weight of the arrow itself can, within limits, be selected for speed. However, the size of the vanes used on the arrow to stabilize it in flight cannot be reduced excessively without adversely affecting the flight performance of the arrow. Means have been sought to further increase arrow speed without interfering with its stability in flight and thus its ability to fly accurately shot after shot.
In order for an arrow to fly properly, with a maximum of speed and accuracy, it must be properly spined relative to the draw weight of the bow and the actual propulsion force placed on it by the bow string during release of the arrow. By spine is meant the degree of flexibility of the arrow shaft. This in turn depends on the wall thickness and diameter of the arrow shaft, its length and the materials from which the shaft is made. The shaft should bend enough to clear the bow without striking it during shooting of the arrow, but not enough to cause the arrow to fly inaccurately. Arrow shafts are manufactured with various spines to suit individual needs.
In fine tuning a bow for maximum shooting efficiency it is sometimes necessary to change the spine of the arrow. It is impractical to vary the shaft length, as by shortening it, to change the arrow spine. However, arrow spine can also be changed by increasing the weight of the arrow pile to weaken the arrow spine or by decreasing that weight to strengthen the arrow spine. It is conventional to change arrow piles, that is, substitute standard length piles or long heavy piles, as needed. This is expensive, requiring a new set of piles for the arrows. Therefore, it would be desirable to provide improved means for accomplishing the desired effect.
Consideration should also be given to means for providing proper weight distribution at the arrow pile. Such weight distribution affects balance and therefore arrow flight. Conventional target piles come in only a few standard lengths per arrow size and offer no adjustability. An arrow pile readily adjustable in weight distribution as well as weight would permit improved ease of fine tuning.
In originally inserting and/or changing arrow piles in arrows, considerable difficulty is often encountered because of normal variations in the internal diameter of the arrow shaft. Although a close fit is desired between the pile and shaft so as to prevent loosening and loss of the pile when removing the arrow from dense targets, too close a fit makes insertion in and removal of the pile tube from the shaft difficult. It would be desirable to be able to provide means for adjusting the pile to properly fit the arrow shaft.